WHSL Systematic Reviews: Systematic Reviews

What is a systematic review?

Systematic reviews are a type of literature review that collects and critically analyzes multiple research studies or papers, using methods that are selected before one or more research questions are formulated, and then finding and analyzing studies that relate to and answer those questions in a structured methodology. They are designed to provide a complete, exhaustive summary of current literature relevant to a research question. Systematic reviews of randomized controlled trials are key in the practice of evidence-based medicine, and a review of existing studies is often quicker and cheaper than embarking on a new study.An understanding of systematic reviews, and how to implement them in practice, is highly recommended for professionals involved in the delivery of health care.¹

Syntheses of the literature are comprised of many different forms, of which systematic reviews are just one such type of synthesis. Systematic reviews are used to summarize evidence about a specific and focused health question in which the primary research is examined in an attempt to identify all available literature on the topic. They are most often used to answer foreground questions in evidence-based practice. A systematic review summarizes the results of many studies, and is not simply a summary or overview (review article). A review is a narrative article, whereas a systematic review has rigorous requirements for use in evidence-based medicine (see Definitions). A systematic review is a thorough, comprehensive and explicit way of interrogating the medical literature.

A systematic review is therefore a structured overview with an explicit approach to the control of bias. A systematic review will have a clearly defined clinical question, inclusion criteria, search strategy, and appraisal rules for the evidence contained in the literature that is retrieved. The research found in the literature is critically assessed and evaluated.

Systematic reviews include several steps:

A precise formulation of the problem

Identification of one or more databases to search

Efficient search strategies

Rigorous appraisal of the research designs, implementations and analyses

Systematic (not merely selective) synthesis of information

Justified conclusions

Identification of gaps in present knowledge

Abstracting the data in a standardised format

Systematic reviews are regarded as the "Gold Standard" of evidence in the literature.

What is a meta-analysis?

A meta-analysis is a type of systematic review that uses quantitative methods to combine results from multiple studies. A meta-analysis will yield a summary estimate of effect size and confidence interval around that summary estimate.

A meta-analysis is a statistical approach to combine the data derived from a systematic-review. Therefore, every meta-analysis should be based on an underlying systematic review, but not every systematic review leads to a meta-analysis.

Systematic Review Definitions

The consolidation of research evidence that incorporates a critical assessment and evaluation of the research (not simply a summary) and addresses a focused clinical question using methods designed to reduce the likelihood of bias.

The identification, selection, appraisal, and summary of primary studies addressing a focused clinical question using methods to reduce the likelihood of bias.